Hey all! Dex is getting along just fine and more spoiled than ever , if that's even possible

Anyway, I've been reading about yorkie coloring and wante to get your alls opinion.
When I got dex he was VERY black with the tan markings on face and legs.
Well since then his head has changes to a lighter tan and around his face turned a blueish color, but his body is still really black!
He has some white looking hairs intermittently spread on his body but still dark black.
He will turn one in less than a month

From anyone's experience is this normal, will he ever change to a slate blue color? It doesn't matter to me either way.
He also has a little white patch on his chest

His coat is, I would assume, cotton type.